Dr. Tannen’s Research Review:
In this important research article published in Investigative Ophthalmology and Visual Science in March 2011, it is shown that children with amblyopia have significantly poorer “reach” and “grasp” skills compared to normally sighted children at all ages tested. The acquisition of precise eye-hand coordination for reaching, grasping, and manipulating objects is essential to many of our everyday activities. It is seen as an important prerequisite for development of perceptual skills that are essential for action planning in hand movement and visual guidance. It is postulated that the lack of stereopsis in amblyopic children is at the root cause of the eye-hand coordination deficits and that restoring binocularity in children with amblyopia may improve their poor eye-hand action control.
Purpose: To investigate whether binocular information provides benefits for programming and guidance of reach-to-grasp movements in normal children and whether these eye-hand coordination skills are impaired in children with amblyopia and abnormal binocularity.
Methods: Reach-to-grasp performance of the preferred hand under binocular versus monocular (dominant or non-dominant eye occluded) conditions to different objects (2 sizes, 3 locations, 2-3 repetitions) was quantified using a 3D motion-capture system. Participants were 36 normally-sighted children (aged 5-11) and 11 adults, and 21 children (aged 4-8) with strabismus and/or anisometropia. Movement kinematics and error rates were compared for each viewing condition within- and between-subject groups.
Results: The youngest control subjects employed a mainly programmed (ballistic) strategy and collided with the objects more often when viewing with only one eye, while older children progressively incorporated visual feedback to guide their reach and, eventually, their grasp, resulting in binocular advantages for both movement components resembling those of adult performance. Amblyopic children were the worst performers under all viewing conditions, even for the dominant eye. They spent almost twice as long in the final approach to the objects and made many (1.5-3 times) more errors in reach direction and grip positioning as their normal counterparts, these impairments being most marked in those with the poorest binocularity, regardless of the severity or cause of their amblyopia.
Conclusions: The importance of binocular vision for eye-hand coordination normally increases with age and use of ‘on-line’ movement guidance. Restoring binocularity in children with amblyopia may improve their poor hand action control.
+ Author Affiliations
- 1Department of Optometry & Visual Science, The Henry Wellcome Laboratories for Visual Sciences, City University, Northampton Square, London EC1V 0HB, UK.
- 2 School of Optometry and Vision Science, University of New South Wales, Sydney, NSW 2052, Australia.
- 3 Moorfields Eye Hospital, 162 City Road, London EC1V 2PD, UK.
- Copyright © 2010 by Association for Research in Vision and Ophthalmology